A search of the prior art uncovered U.S. Pat. Nos. 1,844,308, 3,344,854, 3,989,101, 4,066,119, 4,076,072 and 4,405,013. U.S. Pat. No. 3,344,854 discloses an engine radiator having a movable endless belt screen around the heat exchanger for preventing clogging of heat exchangers by foreign particles entrained in the cooling medium.